An 1852 Assay Office $50 coin is the headline lot of Heritage Auctions' December 4-7 sale at the Houston Money Show, with an opening bid of $337,500.
The lot was issued by the United States Assay Office, which was founded in San Francisco during the gold rush era.
At the time the state of California lacked a branch mint and the office stepped in to fill the gap.
The present lot is the only PCGS MS64-graded slug known to exist and is thought to have belonged to chief assayer Augustus Humbert.
It first sold in 1909 for $220, later achieving $50,000 in 1993. It last sold in April for $411,250, equating to growth of 10.5% pa over the past 21 years.
A 1652 New England shilling is also on offer, with a minimum bid of $270,000.
The coins are among the first ever issued in North America and were produced by British colonists in Massachusetts.
The Mint Act of May 27, 1652 was the catalyst for the project, stating: "all persons whatsoever have liberty to bring into the mint house at Boston all bullion plate or Spanish coin."
There they were melted down and remade.
We have a stunning selection of rare coins available, click here to take a look.
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